Who is Teresa Sharpe from Sharpe's Skirmish and what is their importance?

Teresa is Captain Sharpe's wife. She is described as a thin-faced, good-looking, young woman, who killed the French after they killed her family. Her nickname is La Aguja, the needle, because she preffered method of killing uses a stiletto. Teresa and Sharpe have an infant daughter named Antonia, who resides in Salamanca. When the French attack San Miguel, Teresa rides to Salamanca to call for reinforcements.